1. Field of the Invention
The invention relates to the field of conventional printing on a rotary printing machine (for example offset, gravure, flexo or screen printing) and more particularly to a sleeve-like form for a printing or transfer cylinder including a support sleeve having an inner circumference and a pair of longitudinal ends.
The invention also relates to a device for chamfering the longitudinal ends of such a sleeve-like printing or transfer form.
2. Description of the Related Art
In the current sleeve technique for channel-less printing—in particular with rubber blanket and printing form, but also other printing processes—it is usual, in order to fit the sleeve-like printing or transfer form to a printing cylinder, to push the printing or transfer form onto the printing cylinder as it is widened by means of compressed air. The removal of the compressed air has the effect of placing the printing or transfer form on the printing cylinder with a form fit, on the principle of a shrink fit. By means of the renewed supply of compressed air, the printing or transfer form can be removed from the printing cylinder again.
Sleeves of this type, that is to say sleeve-like printing or transfer forms are generally built up from a support sleeve made of a metallic material, onto which the corresponding coating is applied. From flexographic printing, for example, it is sufficiently well known to apply sleeve-like printing and transfer coatings to nickel sleeves produced by electroplating.
U.S. Pat. No. 5,379,693 discloses a sleeve-like offset printing form or a form sleeve, which is produced from a metal plate cut rectangularly to size, by the edges of the plate pointing towards each other being connected by means of a welded seam. The support sleeve produced in this way is coated and exposed all around, except for the welded seam.
U.S. Pat. No. 5,351,615 discloses a sleeve-like offset rubber blanket or rubber sleeve, which is likewise produced from a tailor-made support plate, to which, in the planar state, a rubber layer is applied, by the start and end of the support plate together with the rubber layer being welded to each other.
When such a sleeve is being pushed onto a printing cylinder, in order to be able to adjust and mount the sleeve accurately and in a fixed position there, provision is generally still made, as indicated for example by EP 0 704 301 B1, of a thin intermediate layer in the form of a self-adhesive film, which is easily replaceable, between the surface of the cylinder core and the inner surface of the sleeve, or else a coating on the surface of the cylinder core, or else as a thin replaceable sleeve. This intermediate layer can also have a thermally insulating effect. The intermediate layer is also known as an Astralon film, with regard to its material.
The sleeve, whose internal diameter is smaller than that of the printing cylinder core, after being precentered, for example by means of a conical taper on the printing cylinder body, is widened mechanically to the larger printing cylinder diameter, so that the sleeve can be pushed completely onto the cylinder body over an air cushion.
Nevertheless, as the sleeve is being pushed onto the printing cylinder body, it may occur that the thin film placed on the latter is scratched by the metallic support sleeve of the sleeve or is damaged by pressure. In particular when the metallic support plate is being cut to size, no deburring of the cut edges has been carried out, and therefore the metallic support sleeve has sharp-edged burrs likewise running all around the internal diameter at its longitudinal ends. A thin Astralon film can likewise be damaged by such burrs.